1. Field of the Invention
The present invention relates to a process for producing an aromatic polyether obtainable by polymerizing a biphenol and a dihalogenodiphenyl sulfone in diphenyl sulfone in the presence of an alkali metal carbonate and/or an alkali metal bicarbonate.
2. Description of Related Art
Aromatic polyethers containing a repeating unit represented by the formula (1-1): 
are useful as high molecular compounds superior in heat resistance, impact resistance and others. As processes for producing them, there have been known processes in which 4,4xe2x80x2-biphenol is polymerized with a 4,4xe2x80x2-dihalogenodiphenyl sulfone represented by the formula (2): 
wherein each of x1 and x2 independently represents a halogen, in diphenyl sulfone and in the presence of an alkali metal carbonate and/or an alkali metal bicarbonate to produce an aromatic polyether represented by the formula (1): 
wherein each of x1 and x2 have the same meaning as above, and n represents an integer of 1 or above (JP-A-3-84032).
In the above process, when a 4,4xe2x80x2-dihalogenodiphenyl sulfone (2) is used in an amount exceeding 1 time by mole and not exceeding 1.05 time by mole, aromatic polyethers represented by the above formula (1) having a higher molecular weight, such as those having a weight-average molecular weight of 35,000 or more, can be obtained. However, although an aromatic polyether having such a desired high molecular weight can be obtained, a problem arises that the obtained aromatic polyether has a greater dispersion of molecular weight, which tends towards an inferior impact resistance.
An object of the present invention is to provide a process for producing an aromatic polyether having high molecular weight as well as small dispersion of molecular weight by polymerizing a biphenol with a dihalogenodiphenyl sulfone in diphenyl sulfone and in the presence of an alkali metal carbonate and/or an alkali metal bicarbonate.
Under these circumstances, the inventors have conducted an intensive research for developing a process which allows production of aromatic polyethers with a high molecular weight and a small dispersion of the molecular weight by polymerizing 4,4xe2x80x2-biphenol with a 4,4xe2x80x2-dihalogenodiphenyl sulfone in diphenyl sulfone and in the presence of an alkali metal carbonate and/or an alkali metal bicarbonate. As the result, they have found the fact that the above problems can be solved when the polymerization is carried out at a specific temperature. The inventors have further found that aromatic polyethers having improved transparency can be obtained in the above process by using hypophosphorous acid and/or its alkali metal salts. Thus, the present invention was completed.
Accordingly, the present invention provides a process for producing an aromatic polyether represented by the above formula (1) which comprises polymerizing 4,4xe2x80x2-biphenol with a 4,4xe2x80x2-dihalogenodiphenyl sulfone represented by the above formula (2)
in an amount exceeding 1 time by mole and not exceeding 1.05 time by mole based on said 4,4xe2x80x2-biphenol
in diphenyl sulfone and
in the presence of an alkali metal carbonate and/or an alkali metal bicarbonate
at a temperature which is not lower than 240xc2x0 C. and not higher than 270xc2x0 C.
The present invention further provides a process for producing an aromatic polyether represented by the above formula (1) which comprises polymerizing 4,4xe2x80x2-biphenol with a 4,4xe2x80x2-dihalogenodiphenyl sulfone represented by the above formula (2)
in an amount exceeding 1 time by mole and not exceeding 1.05 time by mole based on said 4,4xe2x80x2-biphenol
in diphenyl sulfone,
in the presence of an alkali metal carbonate and/or an alkali metal bicarbonate and
in the presence of hypophosphorous acid and/or its alkali metal salts in an amount exceeding 0.001 time by mole and not exceeding 0.006 time by mole based on said 4,4xe2x80x2-biphenol at a temperature which is not lower than 240xc2x0 C. and not higher than 270xc2x0 C.